Field of the Invention
This disclosure relates to a vibration type driving device including a vibrator and a driven member and configured to drive the driven member and, more specifically, to a cooling unit of a vibration type driving device.
Description of the Related Art
In the related art, there is a known vibration type driving device configured to drive a movable body (driven member) by vibrations generated by a vibrator. The vibrator generally includes an elastic member and a piezoelectric device, which corresponds to an electro-mechanical energy conversion element arranged on the elastic member.
The driven member that is in press-contact with the vibrator is driven by a traveling wave, which is generated by exciting the vibrator with two standing waves having phases positionally shifted from each other at temporally shifted phases.
The vibration type driving device is demanded to be reduced in size and have high-power. However, in that case, a countermeasure for heat generation and a temperature increase is important.
In other words, a loss of input power of the vibration type driving device, which is not output therefrom, is considered to be changed to heat.
However, when demanding a reduction in size and high-power, an amount of power loss per volume and an amount of power loss per surface area increase.
Such dissipated power causes deterioration in function of the components of the vibration type driving device, and causes a temperature rise as much as it affects the performance of the vibration type driving device, whereby such a phenomenon that components are subjected to acceleration of abrasion occurs. Therefore, it is necessary to prepare a countermeasure such as a cooling unit.
Examples of the cooling unit as described above include a structure having a fan-shaped pressing spring, which brings the vibrator and the driven member into press-contact with each other, to generate an air flow at the time of driving as disclosed in Japanese Patent Laid-Open No. 9-098586.
However, with the configuration in which the shape of the pressing spring of the related art is partly modified into the fan structure does not necessarily achieve a satisfactory result of cooling the vibration type driving device against the reduction in size and high-power, and still has a problem of difficulty in sufficient cooling.
As regards the high-power required for the vibration type driving device, a configuration using a plurality of driven members as illustrated in FIG. 11 is conceivable.
In FIG. 11, driven members 103a and 103b are in contact with a vibrator 101. Therefore, when the driven members 103a and 103b are connected with a common output shaft 106, outputs generated by the plurality of driven members may be obtained from the single output shaft. Consequently, a high-power configuration is achieved.
However, when such a configuration is employed in the disclosed configuration, an air flow generated by a pressing spring fan 117 flows as indicated by an arrow 18 illustrated in FIG. 11, and hence only the driven member on the inner side is cooled. Therefore, sufficient cooling of the entire vibration type driving device is not achieved easily.